This invention relates to apparatus for joining a plurality of beams or struts at a vertex and, more particularly, to such apparatus as used in forming a ribbed frame type of structure upon which a membrane or skin can be supported.
In recent years there has come into widespread use of a type of space frame structure that is free of internal and external support other than the mounting base of the structure, such that the interior of the structure is useful space. There are various forms of such structures, and they are generally known as "geodesic" or "space frame" structures. They find diverse use ranging from small domed storage areas or temporary shelters to huge domed stadiums or auditoriums, as well as flat roof structures.
The individual beam of the described types of structures, typically, although not necessarily, formed of wood or metal, are grouped together in selected geometries, such as triangles, with the vertices of the triangles being joined together at interconnecting hubs. Various types of beam or strut connector systems have been devised for use in geodesic structures. See, for example, U.S. Pat. Nos. 3,186,522; 3,323,820; 3,486,278; 3,635,509 and 3,810,342.
Prior art strut connector systems are found to suffer a number of disadvantages. In some strut connector systems the individual strut connectors and/or strut supports are fairly complicated and, therefore, tend to be expensive and/or difficult to make or field construct. Some systems employ strut supports that require the end of each wooden or metal strut to be cut at a precise oblique angle that is a function of the angle at which the strut is supposed to meet the plane of the hub to which it will ultimately be connected. Also, in most cases a membrane or "skin" of a covering material (for example, plywood or cloth) is generally placed over a ribbed geodesic frame. This being the case, it is desirable that the strut joining apparatus or the hardware used to fasten each strut to its hub or the apparatus to the strut not protrude into the region where the skin of the structure is to be mounted.
It is among the objects of the present invention to provide a strut support system that is sturdy, inexpensive, simple to make and use, and whose use results in a structural frame to which a skin can be readily applied without the interference of protruding hardware.